[Zadatak] Poljski kalkulator (obrnuta poljska notacija)

Code:

stack s;
while (!kraj_izraza) {
   while(trenutni_karakter!=operand)
      s.push(trenutni_karakter);
   ucitaj operand;
   tmp=s.pop() operand s.pop();
   s.push(tmp);
}

Code:

/*
    obrnuta poljska notacija
*/

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <stack>
using namespace std;

int main(void) {
    stack <int> s;
    ifstream ulaz("ulaz.txt");
    char tmp[10];
    memset(tmp,'\0',10);
    while (ulaz>>tmp) {
        if (strlen(tmp)==1 && (tmp[0]=='+' || tmp[0]=='-' || tmp[0]=='*' || tmp[0]=='/')) {
           int rez=0,a,b;
            switch(tmp[0]) {
                case '+':
                    a=s.top();
                    s.pop();
                    rez=a+s.top();
                    s.pop();
                    break;
                case '-':
                    a=s.top();
                    s.pop();
                    rez=a-s.top();
                    s.pop();
                    break;
                case '*':
                    a=s.top();
                    s.pop();
                    rez=a*s.top();
                    s.pop();
                    break;
                case '/':
                    a=s.top();
                    s.pop();
                    rez=a/s.top();
                    s.pop();
                    break;
                    }
            s.push(rez);
            }
        else {
            int t=atoi(tmp);
            s.push(t);
            }
    }
    cout << "Rezultat je: " << s.top() << endl;
    ulaz.close();
    return 0;
}